COMPUTATION OF MINIMUM DO (Cont)

It will take about 0.64 d (roughly 15hours) for the minimum DO to occur.

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Now applying next Streeter-Phelps Model Equation for Dc gives

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Dc= =9.87 X (0.745 – 0.479) + 3.7 X 0.479 = 2.63 + 1.78 = 4.4 mg/L

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The minimum DO in the stream is the difference between saturation DO and the critical oxygen deficit, or 11.0 – 4.4 = 5.6 mg/L. At a velocity of 0.5 ft/s, in 0.64 d the distance downstream for the minimum DO is 0.64 d X 24 h/d X 3600 s/h X 0.5 ft/s = 27659 ft approximately 5 million.